IgM antibodies were scant or absent in both
GVHD and non-GVHD mice (Fig. 3B). The
neutralizing capacity of antibodies present in the
serum at day 28 post-transplant was not signif-
icantly different between GVHD and non-GVHD
groups (Fig. 3C). In contrast, serum isolated
from mice with GVHD at day 28 post-transplant
showed a complete inability to inhibit cell-to-cell
spread of MCMV in vitro (table S1 and fig. S4).
Thus, inhibition of cell-to-cell spread in vitro is
the best indicator of protective capacity in vivo,
suggesting that this is a major mechanism by
which antibodies inhibit viral reactivation and
spread after transplantation.
Mechanistically, antibody-mediated protection
can also operate via antibody-dependent cell-
mediated cytotoxicity (ADCC), which requires an
interaction with Fc-receptor–expressing cells. No
reactivation was observed in latently infected
mice that received FcgRIII-deficient grafts
and immunodepletion (Fig. 3D). Thus, the pro-
tection mediated by MCMV antibodies occurs
independently of donor FcgRIII-mediated
ADCC.GVHD results in long-term cellular immuno-
deficiency and impaired pathogen-specific im-
munity ( 20 ). The B cell compartment is slow to
reconstitute and B cell numbers can take sev-
eral years to return to normal, leaving recipients
with impaired humoral immunity ( 14 , 21 ). Mature
splenic B cells (Fig. 3E) and plasma cells in BM
(Fig. 3F) were significantly reduced in latently
infected recipients with GVHD, as compared
with non-GVHD mice. Plasma cells are long-lived
and reported to be radiation-resistant ( 22 ). How-
ever, plasma cell numbers were greatly reducedMartinset al.,Science 363 , 288–293 (2019) 18 January 2019 4of6
Fig. 3. MCMV reactivation in GVHD
correlates with reduced levels of
MCMV-specific antibodies.(A) MCMV-
specific neutralizing antibodies (top)
and MCMV-specific IgM and IgG
quantification (bottom) in latently
infected B6D2F1 mice pre-transplant
(n= 6 per group) are shown.
(BtoH) Latently infected B6D2F1 mice
were transplanted with B6 TCD-BM
(non-GVHD) or BM + T cells (GVHD).
(B) MCMV-specific IgM and IgG
quantification at days 7 and 28 post-
transplant (n= 6 per group) is shown.
MCMV-specific IgG titers, calculated
as described in the supplementary
materials and methods, together with
statistical analysis, are shown in the
far right graph. Data are representative
of two experiments wheren=4mice
per group. (C) Levels of neutralizing
antibodies at days 7 and 28 post-
transplant (non-GVHD,n= 11; GVHD,
n= 12) are shown. Data are combined
from two experiments with 5 or 6 mice
per group per experiment. (D) Latently
infected B6D2F1 hosts were transplanted
with B6.WT or B6.FcgRIII−/−,TCD-BM
(non-GVHD), or BM + T cells (GVHD),
and treated with the anti-CD4, -CD8,
and -NK1.1 depleting antibodies, as indi-
cated. Viremia at 4 weeks post-transplant
is shown.n> 8 per group from two
experiments with 4 or 5 mice per group
per experiment. The number of
(E) mature B cells in the spleen and
(F) plasma cells in BM of latently infected
B6D2F1 mice 14 days post-transplant
(non-GVHD,n= 7; GVHD,n=8)is
shown. Data are combined from two
experiments with 3 or 4 mice per group
per experiment. Nontransplanted
controls are shown for comparison.
(G) The relative contributions of host and
donor cells to the plasma cell pool are
shown. (H) The number of IgG2A+plasma
cells in BM is shown (non-GVHD,n=7;
GVHD,n= 8). Data are combined
from two experiments with 3 or 4 mice
per group per experiment. Data represent
mean ± SEM. *P<0.05,**P<0.01,
***P< 0.001 (Mann-WhitneyUtest).RESEARCH | REPORT
on January 17, 2019^http://science.sciencemag.org/Downloaded from